It is known to provide a phase shift controlled full bridge DC-DC converter which comprises four switches, typically constituted by MOSFETs, arranged in a bridge with a DC supply connected to one diagonal of the bridge and a primary winding of a transformer connected to the other diagonal of the bridge. A DC output of the converter is provided via a full wave rectifier arrangement, for example comprising two diodes connected to a center tapped secondary winding of the transformer, and an output filter comprising a series inductor and a shunt capacitor.
It is also known in such a converter to provide an inductor in series with the primary winding of the transformer, and a snubber capacitor connected in parallel with each of the four switches, in order to provide ZVS of the switches when the converter operates with its full load. However, such an arrangement fails to ensure ZVS at reduced loads of the converter, and has other disadvantages such as requiring an increased inductance of the output filter inductor.
An object of this invention is to provide an improved full bridge DC-DC converter.